1. Field of the Invention
This invention relates to a system for stabilizing a spinning spacecraft exposed to destabilizing moments and/or possessing unfavorable mass properties.
2. Description of Related Art
Spin stabilization is the simplest technique for controlling spacecraft attitude for orbiting spacecraft during the launch and orbit injection phases, and the on-station orbiting phase. A spacecraft (or any other generally rigid body) can be characterized as having three principal moment of inertia axes which typically each have a unique moment of inertia value, thus defining a maximum axis, a minimum axis, and an intermediate axis. A continuing problem in spacecraft design is to insure spacecraft stability during rotation. In order to provide stability, spacecraft are spun about either a maximum principal axis which is preferred because it is passively stable, or their minimum principal axis, which provides stability if used with active nutation control systems. Rotation about the intermediate axis is inherently unstable and requires a continuous active thruster control system. Since design constraints in spacecraft design often result in spin being preferred about the intermediate or minimum axes, some form of nutation control system is ordinarily required Such systems, however, add complexity, cost and weight to the spacecraft.
In view of the foregoing, there is a need to provide a simplified spacecraft stabilization system permitting rotation about moment of inertia axes other than the maximum moment of inertia axis in a passively stable manner.